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INTRODUCTION
Photovoltaic (PV) panels are often used for agricultural operations, especially in remote areas or where the use of an alternative energy source is desired. In particular, they have been demonstrated time and time again to reliably produce sufficient electricity directly from solar radiation (sunlight) to power livestock and irrigation watering systems.
A benefit of using solar energy to power agricultural water pump systems is that increased water requirements for livestock and irrigation tend to coincide with the seasonal increase of incoming solar energy. When properly designed, these PV systems can also result in significant long-term cost savings and a smaller environmental footprint compared to conventional power systems.
The volume of water pumped by a solar powered system in a given interval depends on the total amount of solar energy available in that time period. Specifically, the flow rate of the water pumped is determined by both the intensity of the solar energy available and the size of the PV array used to convert that solar energy into direct current (DC) electricity.
The principle components in a solar-powered water pump system include:
• The PV array and its support structure,
• Solar charge controller,
• Battery,
• Inverter,
• Programmable timer-switch,
• An electric- powered pump set.
It is important that the components be designed as part of an integrated system to ensure that all the equipment is compatible and that the system operates as intended. It is therefore recommended that all components be obtained from a single supplier to ensure their compatibility.
1.1 NECESSITY:
Solar energy is radiant light and heat from the Sun harnessed using a range of ever-evolving technologies such as solar heating, photovoltaic, solar thermal energy, solar architecture and artificial photo synthesis. It is an important source of renewable energy and its technologies are broadly characterized as either passive solar or active solar depending on the way they capture and distribute solar energy or convert it into solar power. Active solar techniques include the use of photovoltaic systems, concentrated solar power and solar water heating to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favourable thermal mass or light dispersing properties, and designing spaces that naturally circulate air. The large magnitude of solar energy available makes it a highly appealing source of electricity. The United Nations Development Programme in its 2000 World Energy Assessment found that the annual potential of solar energy was 1,575–49,837exa joules (EJ). This is several times larger than the total world energy consumption, which was 559.8 EJ in 2012.
The Earth receives 174,000 terawatts (TW) of incoming solar radiation (insolation) at the upper atmosphereApproximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and land masses. The spectrum of solar light at the Earth's surface is mostly spread across the visible and near-infraredranges with a small part in the near-ultraviolet. Most people around the world live in areas with insolation levels of 150 to 300 watts per square meter or 3.5 to 7.0 kWh/m2 per day.
Solar radiation is absorbed by the Earth's land surface, oceans – which cover about 71% of the globe – and atmosphere. Warm air containing evaporated water from the oceans rises, causing atmospheric circulation or convection. When the air reaches a high altitude, where the temperature is low, water vapour condenses into clouds, which rain onto the Earth's surface, completing the water cycle. Thelatent heat of water condensation amplifies convection, producing atmospheric phenomena such as wind, cyclonesand anti-cyclones .Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature of 14 °Cabby photosynthesis green plants convert solar energy into chemically stored energy, which produces food, wood and the biomass from which fossil fuels are derived.
METHODOLOGY:
Initially we have designed the circuit diagram for installing the solar pump, as we are aware that solar panels never gives us a constant voltage i.e., output at 100 % instead it gives an a variable voltage, to overcome this problem we are planning for an "Charge controller". The pump controller protects the pump from high- or low-voltage conditions and maximizes the amount of water pumped in less than ideal light conditions. An AC pump requires an inverter, an electronic component that converts DC electricity from the solar panels into AC electricity to operate the pump.
1.5 SCOPE OF THE PROJECT:
With advancements in technology, the systems can be made more user-friendly. You can control the motor pump from a remote location using your mobile phone. You can get water level indication of the reservoir and overhead storage tank in your mobile phone. These technologies are already available in the market, though presently they are not so popular.
For further information on this subject you may refer to ‘Irrigation Automation Opportunities in Rural Areas’ article published in January 2012 issue. Also, you may refer to DIY articles on related topics, such as ‘Cellphone-Based Remote Controller for Water Pump’ published in January 2013 and ‘GSM-Based Bore well Water-Level Monitor’ published in May 2012 issues.
LITERATURE SURVEY
Photovoltaic (PV) technology is used for generating electricity from the incoming solar radiation. Several attempts have been made to evaluate, monitor and improve the performance of different components of a PV system: a PV module (Abudallah, 2004; Vick and Clark, 2004; Huang and Sun, 2007; Hansen et al., 2000; Lorenzo, 1994), a controller (Ohm and Rupp, 2003), a battery (Colette et al., 1993; Giraud et al., 2003; Achaibou et al., 2012), a pump (Vick and Clark, 2011), and a pump motor (Bhatt et al., 1987). These, and similar studies have been effective for improving the efficiency of the PV system components. However, several factors need to be considered for an optimal PV system design to achieve the desired reliability of the system in a given environment. This involves a detailed investigation of all interacting physical (plant and soil type, irrigation system specifications, PV system sizing, site attributes), meteorological (solar radiation, air temperature, relative humidity, wind speed, precipitation) and managerial (irrigation scheduling) variables with the aim of achieving the desired reliability of the PV system. Ultimately, a technique that combines the center pivot irrigation system characteristics, daily crop water requirements, soil moisture status, irrigation applications, PV array output, load demands, and energy storage is required for evaluating a solar-powered center pivot irrigation system in terms of its reliability. This sort of holistic approach could be very beneficial for effective sizing of the system.
The setup of a PV system is also very flexible. The most efficient use of solar energy is when the panels are directly connected to the load. In fact, the success of water pumping lies partly with the elimination of the intermediate phase, namely the battery bank, for energy storage. With a direct connection between the PV array and the pump, water can be pumped during sunlight hours. The most efficient form of direct-connect systems is when the water is being pumped to an elevated storage tank, thus the electrical energy from the panels is converted to potential energy of the elevated water, to be used on demand, often by gravity (Hamid at et al., 2003). The overall efficiency, from sunlight to water flow, has been recorded to exceed 3% (Dad and Mahmoud, 2005; Palfrey et al., 1987).
This system is easy to implement and environment friendly solution for irrigating fields. The system was found to be successful when implemented for bore holes as they pump over the whole day. Solar pumps also offer clean solutions with no danger of borehole contamination. The system requires minimal maintenance and attention as they are self-starting. To further enhance the daily pumping rates tracking arrays can be implemented. This system demonstrates the feasibility and application of using solar PV to provide energy for the pumping requirements for sprinkler irrigation. Even though there is a high capital investment required for this system to be implemented, the overall benefits are high and in long run this system is economical (Harishankar et al., 2014).
Water pumping has long been the most reliable and economic application of solar-electric (photovoltaic, or PV) systems. Most PV systems rely on battery storage for powering lights and other appliances at night or when the sun is not shining. Most PV pumping systems do not use batteries – the PV modules power the pump directly. Without batteries, the PV pumping system is very simple. It consists of just three components: the solar array, a pump controller and the pump. The only moving part is the pump. The solar modules are warranted to produce for 20-25 years. The expected life of most controllers is 5-10 years. Pump life can vary from 5 - 10+ years (and many are designed to be repaired in the field). Unless the pump or controller fails, the only maintenance normally required is cleaning the solar modules every 2- 4 weeks! This task obviously can be done cheaply by no skilled local labor (Aligarh 2011). Recently Hammed, 1999, presented a study related to the usage of photovoltaic generated electricity for pumping water from 13 wells spread across the east and south east desert which is far from the national grid, as well as in the southern parts of the Jordan which has a complicated topographical situation. These pumps are capable of pumping 40–100 m3 of water per day individually to meet the daily demands of individuals living in those areas. A fully automated irrigation system is designed, built and tested using solar PV cells and a digital controller. The system is economical, reliable, portable, and compact. Savings in electricity bills and water bills can justify the initial cost, which may be a bit more than the conventional system, over a period of time. It causes less damage to the environment and releases the public utilityfrom an extra load. It can be used in small or big farms, gardens, parks and lawns. Also, it can be used as a universal solar-based-controller to control building doors, water heaters, and air-conditioning control systems (Ali 2001).
The solar water-pumping technology is commercially available, has-proven record of reliability, require, minimal skilled manpower once in operation, and operation and maintenance cost is also very minimal and affordable. The photovoltaic pumps have many advantages including they operate on freely available sunlight and therefore incur no fuel or electrical costs. They are also environmentally friendly, reliable and have a long working life (Yingdong 2011). The advantage of using solar energy for pumping the water is that major quantities of water are required during day time and that too during time when the sun is on top of our head, and during these times the PV panels produce maximum energy and hence the water quantity. These solar pumps can be installed in locations which are not connected to national electric grid (Ahmet 2012).
PV systems for the pumping of groundwater are also used in Upper Egypt, proving that the cost of the water unit pumped by PV systems is significantly lesser than that pumped by diesel systems (Yingdong 2011). 9 million pump sets for irrigation run by diesel out 21 million pump sets in India (3.73 KW (5 HP)). Out of these 9 million diesel pump sets 75% are assumed to be in solar resource region; total number of diesel pump sets in solar resource region comes to 6.75 million. Out of 6.75 million diesel pumps, 70% have land for installation of PV System; total numbers of pump sets in solar resource region and have land for installation of solar PV comes to 4.725 million ie 16,785 MW (just half of diesel pumps). The replacement of 4.5 million diesel pumps saves 223,800 million liter of diesel and 469.98 billion kg carbon dioxide per annum (Arora 2013). The procedures reported above have shown that the optimal nominal electric power of the PV generator, for reference parameters in the Arilje region, with decade average daily water requirements of 12.8 m3 ha–1 day–1, that would satisfy the raspberry demands throughout the entire irrigation observed period, (Gajic et al., 2013 ). At annual operation of 2000 hours, Claro Energy's 8.5 kW solar pumps costing Rs. 1 million will save some 17000 kWh of electricity each per year valued at Rest. 85000/year (Mukherji., 2007).
SYSTEM COMPONENTS
The whole system of solar water pumping includes the following components. they are,
• The PV array and its support structure,
• Solar charge controller,
• Battery,
• Inverter,
• Programmable timer-switch,
• An electric- powered pump set.
SOLAR PANEL
Photo voltaic (PV) is the name of a method of converting solar energy into directcurrentelectricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon commonly studied in physics, photochemistry and electrochemistry. A photovoltaic systememploys solar panels composed of a number of solar cells to supply usable solar power. The process is both physical and chemical in nature, as the first step involves the photoelectric effect from which a second electrochemicalprocess takes place involving crystallized atoms being ionized in a series, generating an electric current. Power generation from solar PV has long been seen as a cleansustainable energy technology which draws upon the planet’s most plentiful and widely distributed renewable energy source – the sun. The direct conversion of sunlight to electricity occurs without any moving parts or environmental emissions during operation. It is well proven, as photovoltaic systems have now been used for fifty years in specialized applications, and grid-connected PV systems have been in use for over twenty years. They were first mass-produced in the year 2000, when German environmentalists including Eurosolarsucceeded in obtaining government support for the 100,000 roofs program.
Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaic has declined steadily since the first solar cells were manufactured, and the liveliest cost of electricity from PV is competitive with conventional electricity sources in an expanding list of geographic regions.Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries. With current technology, photovoltaic recoups the energy needed to manufacture them in 1.5 to 2.5 years in Southern and Northern Europe, respectively.
Solar PV is now, after hydro and wind power, the third most important renewable energy source in terms of globally installed capacity. More than 100 countries use solar PV. Installations may be ground-mounted (and sometimes integrated with farming and grazing) or built into the roof or walls of a building (either building-integratedphotovoltaic or simply rooftop).
In 2014, worldwide installed PV capacity increased to at least 177 gig watts (GW), sufficient to supply 1 percent of global electricity demands. Due to the exponential growth of photovoltaic, installations are rapidly approaching the 200 GW mark – about 40 times the installed capacity of 2006. China, followed by Japan and the United States, is the fastest growing market, while Germany remains the world's largest producer, with solar contributing about 7 percent to its annual domestic electricity consumption.
4.1 WORKING OF PV PANEL:
Solar cells are running on junction effect principle. To understand junction effect, we should understand n-type and p-type material. Doping process is needed to obtain n-type or p-type material. Doping means inserting another atom into the bulk crystal. Consider silicon crystal: each silicon atom has four electrons in its valance band and these electrons make bonds with other Silicon atom. You can see the silicon crystal in the left side with valance electrons of each Si atom. Note that we call that structure as crystal since all Si atoms are perfectly aligned. We can convert this structure in to n-type or p-type by doping different atoms. For example let’s dope it by boron. Boron atom has 3 electrons in its valance band. When we insert B atom instead of a Si atom, one bond between B atom and a Si atom will be very weak. To complete the prefect symmetry in this structure, crystal will be aimed to catch an external electron. As you can see an electron is missing since B atom has 3 electronsin its valence band. This missing bond can be treated a positively charged particle called ‘hole’. This material is called p-type material. What if we dope Phosphorous atom instead of Boron atom? Phosphorous atom has 5 electrons in its valance band.
When P atom is inserted into the Si lattice, 4 electrons will be able make bond with neighbor Si atoms. However 5th electron will be hanged on. So, it will be in an energy level that very close to conduction band since it will be nearly free. This nearly free electron can easily leave P atom with a small thermal energy. Note that there is an extra electron in this new structure. So we call this new material n-type material. In contrast to p-type material, n-type material has a tendency to give electrons. Consequently we have two types of materials. One wants to give electrons and the other wants to receive electrons. We can create a p-n junction by bringing them together.
P –n junction:
When we bring p-type and n-type material together, diffusion occurs on the surface between them. An electron starts to diffuse from n-type to p-type. Similarly, holes diffuse from p-type region to n-type region. This diffusion creates an electron-hole free region in a very short distance at the interface region. This thin layer is called depletion region
• Amorphous
Mono crystalline(single-crystalline silicon):
Solar cells made of monocrystalline silicon (mono-Si), also called single-crystalline silicon (single-crystal-Si), are quite easily recognizable by an external even colouring and uniform look, indicating high-purity silicon.
Mono crystalline solar cells are made out of silicon ingots, which are cylindrical in shape. To optimize performance and lower costs of a single mono crystalline solar cell, four sides are cut out of the cylindrical ingots to make silicon wafers, which is what gives mono crystalline solar panels their characteristic look.
A good way to separate mono- and polycrystalline solar panels is that polycrystalline solar cells look perfectly rectangular with no rounded edges.
POLYCRYSTALLINE:
The first solar panels based on polycrystalline silicon, which also is known as poly silicon (p-Si) and multi-crystalline silicon (mc-Si), were introduced to the market in 1981. Unlike mono crystalline-based solar panels, polycrystalline solar panels do not require the Czochralski process. Raw silicon is melted and poured into a square mold, which is cooled and cut into perfectly square wafers.
AMORPHOUS SILICON(a-Si):
Because the output of electrical power is low, solar cells based on amorphous silicon have traditionallyonly been used for small-scale applications such as in pocket calculators. However, recent innovations have made them more attractive for some large-scale applications too.
With a manufacturing technique called “stacking”, several layers of amorphous silicon solar cells can be combined, which results in higher efficiency rates (typically around 6-8%).
Only 1% of the silicon used in crystalline silicon solar cells is required in amorphous silicon solar cells. On the other hand, stacking is expensive.
4.2 MONO CRYSTALLINE SOLAR CELL:
Mono crystalline photovoltaic electric solar energy panels have been the go-to choice for many years. They are among the oldest, most efficient and most dependable ways to produce electricity from the sun.
Each module is made from a single silicon crystal, and is more efficient, though more expensive, than the newer and cheaper poly crystalline and thin-film PV panel technologies. You can typically recognize them by their colour which is typically black or iridescent blue.